This section provides background information related to the present disclosure which is not necessarily prior art.
In view of consumer demand for 4WD and AWD motor vehicles, a large number of power transfer systems are currently utilized in vehicular applications for selectively and/or automatically transmitting rotary power (i.e., drive torque) from the powertrain to all four wheels. In most power transfer systems, a power transfer assembly is used to deliver drive torque from the powertrain to one or both of the primary and secondary drivelines. The power transfer assembly is typically equipped with a torque transfer clutch that can be selectively actuated to shift operation of the power transfer system between a two-wheel drive mode and a four-wheel drive mode. In the two-wheel drive mode, drive torque is only transmitted to the primary driveline while drive torque can be transmitted to both of the primary and secondary drivelines when the vehicle is operating in the four-wheel drive mode.
In most 4WD vehicles, the power transfer assembly is a transfer case configured to normally transmit drive torque to the rear driveline and to selectively/automatically transfer drive torque through the torque transfer clutch to the front driveline. In contrast, in most AWD vehicles, the power transfer assembly is a power take-off unit (PTU) configured to normally transmit drive torque to the front driveline and to selectively/automatically transfer drive torque through the torque transfer clutch to the rear driveline.
Many power transfer assemblies are equipped with an adaptively-controlled torque transfer clutch to provide an “on-demand” power transfer system operable for automatically biasing the torque distribution ratio between the primary and secondary drivelines, without any input or action on the part of the vehicle operator, when traction is lost at the primary wheels. Modernly, such adaptively-controlled torque transfer clutches are configured to include a multi-plate friction clutch and a power-operated clutch actuator that is interactively associated with an electronic traction control system having a controller and a plurality of vehicle sensors. During normal operation, the friction clutch can be maintained in a released condition such that the power transfer assembly only transmits drive torque from the powertrain to the primary wheels for establishing the two-wheel drive mode. However, upon detection of conditions indicative of a low traction condition, the power-operated clutch actuator is actuated to engage the friction clutch and deliver a portion of the total drive torque to the secondary wheels, thereby establishing the four-wheel drive mode.
In virtually all power transfer systems of the types noted above, the secondary driveline is configured to include a propshaft and a drive axle assembly. The propshaft is drivingly interconnected between an output of the torque transfer clutch and an input to the drive axle assembly. Typically, a hypoid gearset is used to transmit drive torque from the propshaft to a differential gear mechanism associated with the drive axle assembly. The differential gear mechanism may include a differential carrier rotatably supported in a differential housing portion of an axle housing and which drives at least one pair of bevel pinions which, in turn, are commonly meshed with first and second output bevel gears that are connected to corresponding first and second axleshafts for driving the secondary wheels. The hypoid gearset typically includes a ring gear and a pinion gear meshed with the ring gear. The pinion gear is formed integrally with, or fixed to, a pinion shaft that is rotatably support by a cartridge-type bearing unit in a pinion housing portion of the axle housing. The pinion shaft is typically connected via a shaft coupling component of a coupling device, such as a universal joint, to the propshaft. The ring gear is typically fixed for rotation with the differential carrier. Due to the axial thrust loads transmitted through the hypoid gearset, it is common for the bearing unit to include at least two laterally-spaced bearing assemblies to support the pinion shaft for rotation relative to the pinion housing portion of the axle housing. Conventional arrangements for rotatably mounting the pinion shaft in the drive axle assembly are shown in U.S. Pat. No. 6,544,140 and International Publication No. WO2013/043202.
While such conventional pinion shaft and coupling support arrangements are adequate for their intended purpose, a need still exists to advance the technology and structure of such products to provide enhanced configurations that provide improved efficiency, reduced weight, and reduced packaging requirements.